NEAR-Shoemaker
Full Name: Near Earth Asteroid Rendezvous - Shoemaker
Phase: Past
Launch Date: February 17, 1996
Mission Project Home Page: http://near.jhuapl.edu/
Program(s): Discovery
The Near Earth Asteroid Rendezvous - Shoemaker (NEAR Shoemaker), named in honor of planetary scientist Gene Shoemaker, was designed to study the near Earth asteroid 433 Eros, one of the largest of the near Earth asteroids, from close orbit over a period of one year. The mission was the first-ever to orbit an asteroid and the first to touch down on the surface of an asteroid. The primary scientific objectives of NEAR were to return data on the bulk properties, composition, mineralogy, morphology, internal mass distribution and magnetic field of Eros. Secondary objectives include studies of regolith properties, interactions with the solar wind, possible current activity as indicated by dust or gas, and the asteroid spin state.
The location of NEAR Shoemaker's planned landing site on Eros is shown in this image mosaic taken on December 3, 2000, from an orbital altitude of 200 kilometers (124 miles). In this view, south is to the top and the terminator (the imaginary line dividing day from night) lies near the equator. The landing site (at the tip of the arrow) is near the boundary of two distinctly different provinces, both of which the spacecraft will photograph as it descends.
Image Credit: Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland
The spacecraft was equipped with an X-ray/gamma ray spectrometer, a near infrared imaging spectrometer, a multi-spectral camera fitted with a CCD imaging detector, a laser rangefinder, and a magnetometer. A radio science experiment was also performed using the NEAR tracking system to estimate the gravity field of the asteroid and determine its mass and density.
The NEAR mission sought to answer fundamental questions about the nature and origin of the many asteroids and comets close to Earth's orbit. These "near Earth" objects may contain clues about the formation of Earth, and other planets. Eros' pristine surface offers a look at conditions in space when Earth formed more than 4.5 billion years ago.
NEAR Shoemaker collected data completing the most detailed scientific profile ever of a small celestial body. NEAR's portrait of Eros - a solid, undifferentiated, primitive relic from the solar system's formation - has already answered fundamental questions on a common class of asteroid. NEAR's 160,000 images of Eros have shown that asteroids can be incredibly diverse objects: NEAR scientists spotted more than 100,000 craters, about 1 million house-sized (or bigger) boulders, and a layer of debris resulting from a long history of impacts. Scientists were able to determine that Eros is not a “rubble pile” of loosely bound pieces, but rather a consolidated object. Furthermore, the chemical information gleaned from the mission is helping us to understand how asteroids like Eros are linked to meteorite samples recovered on Earth.
This image was taken from a range of just 250 meters (820 feet) during NEAR-Shoemaker’s decent to the surface. The image is 12 meters (39 feet) across.
NEAR launched on February 17, 1996 and entered into orbit around Eros on February 14, 2000. As its mission neared completion, a decision was made to attempt to land on the asteroid, something the spacecraft had not been designed to do. As it descended, NEAR Shoemaker snapped dozens of detailed pictures during the final three miles (five kilometers), the highest resolution images ever obtained of an asteroid. The camera delivered clear pictures from as close as 394 feet (120 meters) showing features as small as a golf ball. The spacecraft touched down at a gentle 4 mph, just outside the asteroid's large saddle-shaped depression, Himeros. Despite being an orbiter that was not designed to land, NEAR Shoemaker continued operating and communicating. The craft's gamma-ray spectrometer operated for two weeks after the landing, gathering unprecedented data on the elemental composition on and just below the asteroid's surface. NEAR Shoemaker made its last call to Earth on Feb. 28, 2001.